Using the Standardized Antimicrobial Administration Ratios to monitor the influence of antimicrobial stewardship activities

Background: The National Healthcare Safety Network (NHSN) provides an Antimicrobial Use (AU) option to assist antimicrobial stewardship programs (ASPs) with analysis of their AU data. The AU option summarizes data as a Standardized Antimicrobial Administration Ratio (SAAR), an indirectly standardized metric for comparing observed to predicted days of therapy. A key question, and the subject of this study, is whether the SAAR reflects the impact of greater Infectious Disease (ID) physician involvement in prospective audit-and-feedback (PAF).

Methods: The primary ASP activity at our 200-bed hospital is PAF. During the study dates (2013-15), an ID physician met with clinical pharmacists twice a week to discuss audits of broad-spectrum antimicrobials (BSAs). During Phase 1 (baseline – 1/2014), audits were initiated by the clinical pharmacists, and in Phase 2 (2/2014-12/2015), by an ID physician. All audit feedback was communicated to the primary prescriber by the team pharmacist and, if questions arose, by the ID physician. AU data submitted to NHSN were summarized using SAARs for several different groups of antimicrobials.

Results:  The program averaged 61.5 PAF recommendations per month during the 12 months of Phase 2 when process data were collected. The most common feedback to prescribers was to stop antimicrobials (40.4%) or de-escalate therapy (32.4%).

The SAAR decreased across multiple categories during pairwise-years (p<0.0001), with the exception of 2015 vs. 2014 changes in the SAARs for BSAs used for community-acquired infections (p=0.37) and All antibiotic agents (p=0.78) (Table 1). The largest reductions were seen in the SAARs for Anti-MRSA agents and BSAs used for hospital-onset infections.

Conclusion: SAARs were useful in monitoring ASP activities, and declines in SAAR values suggest direct involvement of an ID physician in PAF had a measurable impact on antimicrobial prescribing.

Table 1. Facility-level Standardized Antimicrobial Administration Ratios (SAAR), 2013-2015

Year	SAAR by Antimicrobial Category
	BSAs predominantly used for hospital-onset infections	BSAs predominantly used for community-acquired infections	Anti-MRSA agents	All antibiotic agents
2013	0.96	1.09	1.12	1.09
2014	0.89	0.91	0.98	1.02
2015	0.74	0.93	0.89	1.02